1. Field of the Invention
The present invention relates to a method and an intermediate coating material for forming a layered coated film on an automobile body or the like.
2. Description of the Related Art
As a method for forming a layered coated film on an automobile body, there are known some methods. In one method, coated layers are applied and cured by baking one by one, while in another method, plural coated layers are applied and thereafter they are cured simultaneously. For example, the two-coating and one-baking method is usually conducted for forming a metallic coated film. In addition, in order to improve aesthetic appearance of a top coated film, a method in which a color base coated layer, a metallic base coated layer and a clear coated layer are applied sequentially, and the three layers are cured by baking simultaneously, is also disclosed in Japanese Patent Kokai Publication No. H11(1999)-114489.
On the other hand, small stones are chipped up and hit to a coated film while automobiles are running. This so called “chipping” often peels a coated film from an automobile body. In the conventional method for forming a coated film, the intermediate coated layer was at once cured after being formed on an undercoated film. Thus, it was possible to reinforce chipping resistance of the coated film by, for example, providing an intermediate coated layer specialized to have chipping resistance, or providing an intermediate coated layer modified to have brightness similar to that of a top coated layer so as to make the chipped mark inconspicuous.
For example, in Japanese Patent Kokai Publication No. H6(1994)-256714 or in Japanese Patent Kokai Publication No. H6(1994)-254482, an effort has been made to improve chipping resistance of the intermediate coated film by modifying formulation of a coating material. However, the intermediate coating material does not provide satisfactory appearance and performance when they are employed in the method of simultaneously curing three layers by one-baking.
When three coated layers are formed in the wet-on-wet manner and are cured simultaneously by baking as described above, a baking oven for an intermediate coated layer can be omitted, and therefore great effect is expected economically and environmentally. However, the entire surface of an automobile having considerable concavo-convexes, and when it is coated in the wet-on-wet manner, defects in appearance such as popping and bleeding may occur in some regions.